Find the Difference LeetCode Solution - The Coding Shala

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 In this post, we will learn how to solve LeetCode's Find the Difference Problem and will implement its solution in Java.

Find the Difference Problem

You are given two strings s and t. String t is generated by random shuffling string s and then add one more letter at a random position. Return the letter that was added to t.

Example 1:
Input: s = "abcd", t = "abcde"
Output: "e"
Explanation: 'e' is the letter that was added.

Practice this problem on LeetCode.

LeetCode - Find the Difference Java Solution

Approach 1

Using HashMap.

Java Program: 

class Solution {
    public char findTheDifference(String s, String t) {
        Map<Character, Integer> map = new HashMap<>();
        for(int i=0; i<s.length(); i++) {
            if(map.containsKey(s.charAt(i))) {
                map.put(s.charAt(i), map.get(s.charAt(i))+1);
            } else {
                map.put(s.charAt(i), 1);
            }
        }
        
        for(int i=0; i<t.length(); i++) {
            if(!map.containsKey(t.charAt(i)) || map.get(t.charAt(i)) == 0) {
                return t.charAt(i);
            } else {
                map.put(t.charAt(i), map.get(t.charAt(i))-1);
            }
        }
        //ignore this return;
        return ' ';
    }
}

Approach 2

Using Bit Manipulation.

If we do xor in both the string only additional char will remain.

Java Program: 

class Solution {
    public char findTheDifference(String s, String t) {
        char ch = t.charAt(t.length()-1);
        for(int i=0; i<s.length(); i++) {
            ch ^= s.charAt(i);
            ch ^= t.charAt(i);
        }
        return ch;
    }
}


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